Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
~ 78862
This invention rela-tes to cer-tain organophosphorus
compounds which are useful as stabilizers for polymer
compositions. In a more particular sense it relates to a
method for the preparation of such stabilizers.
The purpose of stabilizers is to prevent
deterioration of the polymers during processing at high
temperatures and also to permit the manufacture of products
with increased intrinsic quality because of the enhancement
of their resistance to thermal and light degradation during
use. In addition 9 because of these enhanced proper-ties,
their versatility is increased and wider use is thereby
made possible.
In the case of vinyl chloride polymers, several
types of stabilizers have been found to be effective.
These include various organic salts of cadmium, calcium,
lead, zinc, barium, strontium, tin, magnesium and antimony,
e.g. stearates, laurates, etc.; mixed metal salts are
especially useful. Dialkyltin compour.ds are also effective.
~espite the recognized ability of these compounds to confer
some stability on these polymers, however, it is well known
that the use of these metal salts, either alone or in
combination with one another, does not in many instances
provide the required resistance to deterioration. The
performance of these metal stabilizers can be enhanced
significantly by adding an organic phosphite to the vinyl
chloride polymer composition.
Many such organic phosphites are available to
serve this purpose. Among them are the bis(alkylphenyl)-
pentaerythritol diphosphites which may have either (or
both) the structures:
:
`'' ~ ' :
` 1~'7~ Z
OCEI \ /~'H 2 \~,
R~30P C~ O ~R
R OCH ;~ C~l ~2 o R
or
~..
R <~)0
R \/CH 2 0\
~ OC 2 ~ 2 ~
p~ CH2 0 ;'
., \;~ ~ ' ' ~ ' '
~ R
where R and R' are each alkyl of 3-10 carbon atoms. These
phosphites provide eminently satis~actory performance because
they tend to inhibit discoloration caused by high tempera~ures
and also because they are themselves quite stable. That is,
they are characterized by a relatively high degree of intrin~ic ;~
stability, especially under conditions of high humidity. This
quality is not normally characteristic of other organic phosphite
stabilizers.
It will be noted that the above phosphites are
"mixed" aryl aliphatic phosphites, i.e., the phosphorus atom is
bound through o~ygen both to aliphatic and to aromatic carbon atoms.;
Phosphites of this type have generally in the past been prepared
by one of two methods: (1) the reaction of an aromatic dichloro-
phosphite with pentaerythritol, as alluded to in Baranauckas et al~
U.S. 3,310~oO9; and (2) the reaction of a phenol with dichloro-
pentaerythritol diphosphite, as shown in Gagliani, U.S. 3,192,243.
Although these methods are useful they each suffer from certain
disadvantages. Thus, method ~1) requires the use of a solvent
because of the very high melting point of pentaerythritol, 253C.
The solvent represents an additional expense and it must be removed
and recovered, all of which adds up to a significant disadvantage.
. ;, .
O 2 _
cm/ph~
~l~7~il62
~ .
Method (2), on the other hand, results in a
product of less than satisfactory purity. A gel permeation
chromatogram of such a product shows as many as five compounds
present in significant quantities and the product's melting curve
is erratic, i.e., it melts (only partially) at a relatively low
ten~erature, then resolidifies, then finally melts completely.
Furthermore, it is a glass and has a tendency to "block", i.e.,
to congeal into hard, intractable lumps, causing shipping and
storage problems.
Friedman, U.S. 3,655,831, shows the reaction of
1,1,3-tris(4-hydroxyphenyl)propane with compounds of the structure ~ ~
'' ' ~.
'` ' ' /OCH2 \ /~' CH2\
R O P\ ~ C\ ~ O R
OCH2 CH2
where ~ is alkyl, such as methyl, or aryl, such as phenyl. In
most instances~ however, the product is polymeric (because both
reactants are multifunctional) and in any event the product
inevitably is a complex mixture of several compounds. Friedman,
U.S. 3,516,363 contains the same teaching.
U.K. 1,180,398 shows the reaction of a tri~sub-
stituted aryl) phosphite and an alcohol (which can be pentaery-
; thritol) to form a product such as that which results from the
process herein. As noted earlier, where pentaerythritol is one
of the reactants its high melting point dictates the use of a
solvent, which in turn presents processing and cost disadvantages.
The same objection is applicable to tha process
disclosed in Hechenbleikner, UOS. 2,847,443; viz., the reaction
of an aromatic dichlorophosphite and pentaerythritol. Both such
reactants as are required to prepare the product of the process
of this invention are solids and a mutual solvent is indicated.
Rattenbury, U.S. 3,576,918, shows the reaction of
diphenylpentaerythritol diphosphite and hydrogenated bisphenol A
cnl/ ~ h, ~ 3 ~
88~Z
i.e., an aliphatic glycol. The product which results is entirely
aliphatic, i.e., there is no aromatic group present at all.
Furthermore, the product is a complex mixture because both
reactants are multifunctional.
Thus, it will be seen that previously known
processes have been characterized either by the production of a
relatively impure product, which requires purification, or by the
necessary use of a solvent. Either of these is an item of sub-
stantial expense.
me present invention comprises a process for
preparing mixed aromatic-aliphatic phosphites comprising mixing a
dipheny]pentaerythritol diphosphite or a dialkylpentaerythritol
diphosphite wherein the alkyl groups contain 1-4 carbon atoms,
with an alkylphenol having the formula
~ OH
Rn
where R is alkyl of 3-10 carbon atoms and n is 1-3, and heating
th~ resulting mixture so as to cause the formation of phenol or a
lower alcohol and to remove such phenol or lower alcohol by dis-
tillation. The product which results from this process is ~ -
relatively pure, i.e., there is no substantial quantity of by-
products; furthermore, the process is simple, requiring no solvent
or unusual steps. -
The substituent groups in the above pentaerythritol
diphosphite most usually are phenyl. Diphenylpentaerythritol - ;
diphosphite is readily available and its transesterification with
phenols proceeds smoothly. The dimethyl compound likewise proceeds
smoothly in such transesterifications and its use is limited only
by its lesser availability and higher cost. The pentaervthritol
diphosphite may be prepared by reaction of pentaexythritol with
triphenyl phosphite or the appropriate trialkyl phosphite, or by
cm/~~
~ 1~7~
reaction of dichloropentaerythritol diphosphite with phenol or
a lower alcohol. In this latter instance, i.e., ~here a lower
alcohol is used, it is necessary for best results that an amine
be employed as an HCl acceptor. The pentaerythritol diphosphite
has either a spiro structure, e.gO,
/OCH2 \~ /`CH20\~ .
C6H50P / \ ,,~OC6H5,
\ OCH2 C~2
or a cage structure, e.g.,
10C6H50~ ~CH20~ ,
POCH2C~H20~ :
C6H5 H20
Gener~lly, pentaerythritol diphosphite compositions are a mixture
of the above two structures, in varying proportions depending upon
the particular method of preparation. Similarly, the bis(alkyl- ;
phenyl~pentaerythritol diphosphites prepared by the process of
this invention usually are a mixture of the spiro and cage
structures illustrated above. -~
The alkylphenol used in the process preferably
is a dialkylphenol because of the unusual thermal and hydrolytic
stability of the mixed aromatic-aliphatic phosphite which results
upon reaction with the substituted pentaerythritol diphosphite.
Especially preferred are those alkylphenols which contain alkyl
groups such as tert-butyl and l,1-dimethylpropyl. Illustrative
species include 2,4-di-tert-amylphenol, 2,4-di-tert-butyl-phenol
and 2,6-di-tert-butylphenol.
Although the reaction will proceed in the absence
of a catalyst it proceeds much more satisfactorily wlth an alkaline
catalyst. Only a small amount is required to serve this purpose,
i.e., from about 0.1 to about 5.0 percent of the total weight of
the process mixture. The catalyst preferably is inorganic, and
most preferably is an alkali or alkaline earth metal compound.
-- 5 --
cm/p~
Illustrative sp~cies includ~ sodium hydroxide, sodium carbonate,
potassium hydroxide, pot~ssium carbonate, lithium caLbonate,
lithium hydroxide, sodium methylate, potassium methylate, sodium
ethylate, calcium hydroxide and barium hydroxide.
The process conditions require merely heating
the reactants to a temperature sufficient to permit distillation
of the displaced phenol or lower alcohol, as the case may be.
A suitable temperature in most instances ranges up to about 210 C.
A solvent may be used and in some instances may afford certain
advantages, but ordinarily it is preferred to carry out the reaction
without a solvent. As the reaction proceeds, phenol (or a lower ;~
alcohol) is distilled, usually at reduced pressure, from the
product mixture.
The desired product is obtained as the residue; it
is obtained as a relatively pure compound contaminated by small
proportions of alkylphenol, tris(alkylphenyl)phosphite and hiyher
molecular welght compounds. An excess of alkylphenol is used in -
the reaction mixture so as to favor completion of the trans- -~
esterification. The excess is of the order of about 5-25~, i.e.,
from about 2.1 to about 2.5 mols of alkylphenol should be used ;
per mol of pentaerythritol diphosphite.
The process of the invention is illustrated by
the following example which should not be regarded as limiting
in any respect.
Example
A mixture of 267 g. (0.75 mol) of diphenyl-
pentaerythritol diphosphite, 371 g. (1.80 mols) of 2,4-di-tert-
butylphenol and 8.5 g. of sodium metbylate is heated with
stirring at reduced pressure for 10 hours. During this time
the temperature is increased and the pressure decreased gradually
to 190C/5 mm. A total of 140 g. (99% of the theoretical amount)
of distillate, identified by it5 set point (38-40C) as phenol,
is obtained by distillation through a packed column as the
-- 6 _ -
cm~p~
~L~788~i2
.. . . . .. .
reaction proceecls. Further heating to a final -temperature of
210C/5 mm. remo~es the unreacted 2,4-di-tert-butyl phenol leaving
450 g. of a product, bis(2,4-di-tert-butylphenyl)pentaerythritol
diphosphite, shown by gel permeation chromatography to have 2.0~
of 2,4-di-tert-butylphenol, and by liquid chromatography to have
3~4% of tris(2,4-.di-tert-butylphenyl).phosphite. Its acid number
is 0.02 and its melting point is 135-150C.
. The efficiency as polymer additives of the
diphosphite products prepared herein is shown by the results of a
test whereby the stabilization of polypropylene, after repeated ~ .
extrusion at high temperatures, is noted. The compositions
tested are as follows: ~.
PARTS coMæoNENTs
lQD Polypropylene
0.05 Calcium .stearate
0.10 Irganox ~ 1010*
to which are added the diphosphites as shown in Table 1. The test
compositi.ons are extruded at 475F from a screw-fed chamber at 76
RPM and a back pressure of 750 psi. The extruded material is
extruded three more times, under the same conditions, and then
separate samples are extruded a fifth time at 475 F and 525F, at
70 R~ and 1000 psi back pressure. After the first and fifth
extrusions the stabilizing effectiveness of the diphosphite
additive is determined by means of a heat aging test. The extruded
test compositions, in the form of 25-mil thick samples, are heated
at 150C in an oven until failure, as noted by sudden crazing,
cracking and/or embrittlement. The time, in hours of heating
required for such failure, is taken as a measure of the stability
of the sample. Data are shown in Table I.
*Tetrakis (methylene-3-{~3',5'-di-tert-butyl-4'-hydroxyphenyl)
propionate}) methane
cm~t)~ , . '
73!~6~ ~
TAB.E I
1st Extrusion 5th Extrusion
Di~ e S~abilizer 4750F 4750F 5250F
.. :
1. 0.07 part of bis- 1340 1267 133
(2~4-di-tert-butylphenyl)-
pentaerythritol diphosphite
2. 0.07 part of bis-(2,6- 1414 1273 1327
di-tert-butylphenyl)pen-
taerythritol diphosphite
It will be noted that the samples are substantially
unchanged, with respect to deteriotation on heating at 150C, even
a~ter five extrusions at high temperature.
Additional test data showing the efficiency of
the diphosphite products herein are contained in Table II. The
data shows the melt index of a test composition immediately after
each of five extrusions at 475 F and 525 F, i.e., a total of ten
extrusions per test composition. The melt indexes are measured
in accordance with the requirements of condition L of ASTM D1238,
i.e., the weight in~grams of the test composition which flows through
an orifice of specified diameter in ten minutes. The test com-
positions are those set out in Table I.
.`'. .:
cm/ ~ h
7~62
-TABLE II
Diphosphite Extrusion -
Stabilizer Temp. 1 2 3 4 5
3. As in 1. 4750F 3.2 3.2 3.2 3.5 3.7
(Table I) 525F 3.2 3.3 3.5 4.0 3.8 :
4. As in 2. 475 F 3.1 3.1 3.4 3.5 3,,7
(Table I) 525F 3.3 3.5 3.7 3,4 3.8
A direct comparison of two polypropylene com-
~ositions, one (No. 1) containing 0.07 part of bis-(2,4-di.-tert-
butylphenyl)-pentaerythritol diphosphite, is shown in Table III.
Each of the two compared compositions contains the following
ingredients:
Parts .Component
100 Polypropylene
--0.05 Calcium stearate
-0.08 Irganox 1010
~The test samples are extruded five times at 525F and the melt
index determined after each extrusion.
TABLE III
.Diphosphite Extrusion
~.Stabilizer . 1 2 3 4 5
2~ 5, None .8.8 10.8 12.6 16.4 20.0
6. As in 1. -4~8 4.9 5.7 6.0 9.0
(Table I)
.All parts herein are by weight unless otherwise
- ~xpressly stated.
~-~cm/~
